Advanced CMOS (complementary metal-oxide-semiconductor) and BiCMOS (bipolar and complementary metal-oxide-semiconductor), as well as some other device technologies, require the formation of doped N or P wells or both N and P wells in bulk silicon or epitaxial (for example, a P.sup.- epi-layer on a P.sup.+ substrate or an N.sup.- epi-layer on an N.sup.+ substrate) wafers. The well formation process is usually based on ion implantation of boron (for P-well) or phosphorus (for N-well) followed by a long (e.g., a few hours), high-temperature (e.g., 1100.degree. to 1200.degree. C.) furnace anneal in an inert or oxidizing ambient.
The relatively long furnace anneal is required to required to form deep N and P well regions via thermal diffusion. The well junction depth is usually at least a few times larger than the source/drain junction depths. For instance, a 0.35 .mu.m CMOS technology may require N and P wells with greater than one micron well-to-substrate junction depth.
If the well formation process is to be performed in a single-wafer-based semiconductor factory, the time and temperature requirements for a single-wafer well drive-in process can be rather excessive (e.g., temperatures of 1100.degree.-1200.degree. C. for more than 30 min.) resulting in low manufacturing throughput. This requirement could make the manufacturing costs unbearably high.
Moreover, conventional furnace diffusion processes for formation of diffused wells cause lateral diffusion of both N and P dopants, resulting in lateral dopant compensation. This undesirable lateral diffusion places a limit on the minimum N-to-P well spacing and makes device layout scaling more difficult.
As a result, there is a need for an RTP (rapid thermal processing) based well formation process which can form the necessary N and P well regions based on reasonable RTP temperature/time conditions. Moreover, there is a need for a well formation process which can form the wells of desired depths using reduced temperature/time process parameters without excessive lateral interdiffusion of the N and P well dopants.